1. Field of the Invention
The invention relates to crosslinkable compositions based on organosilicon compounds that cure by elimination of alcohols to form materials possessing very high stability, methods of producing them, and also to their use.
2. Description of the Related Art
One-component sealant compositions that are storable in the absence of water and cure on admission of water at room temperature by elimination of alcohols to form elastomers are already known. These products are used in large volumes in the building construction industry for example. Polymers terminated by silyl groups bearing reactive substituents such as OH groups, or hydrolyzable groups such as alkoxy groups form the basis for these mixtures. These sealant compositions may further contain fillers, plasticizers, crosslinkers, catalysts and also various additives.
The mechanical properties of the elastomeric products obtained on curing are virtually constant thereafter. This property makes them very useful as joint sealants for example. However, these compositions are frequently also used as coating materials or as adhesives. In such cases, the cured compositions may often be exposed for prolonged periods to the action of both high temperatures and high relative humidities. Under these conditions, the positive range of properties possessed by the cured products may still subsequently change in an undesirable manner.
It is known, for instance, that 1- and 2-component compositions based on crosslinkable organopolysiloxanes having hydrolyzable groups are very quick to irreversibly lose their adherence to glass under the action of heat and moisture. An initial improvement was achieved by using a combination of aminopropyltrimethoxysilane and glycidoxypropyltrimethoxysilane. In addition, DE 196 16789 A1 shows that test specimens stored in hot water do not suffer adhesive failure when the compositions additionally contain not only a silicone resin but also an alkoxysilane comprising a long-chain alkyl radical. Admixture of only one of the two organosilicon compounds alone is insufficient to bring about any improvement in adherence, only the combination of the two additives works.
DE-A1 102007037197 describes compositions based on crosslinkable α-silanes. This reference also mentions the possibility that a multiplicity of monomeric, substituted or unsubstituted silanes may be included a partial hydrolyzate or as a co-hydrolyzate. Specific advantages of selected hydrolyzates are not derived therefrom, however. The exemplary embodiments employ small amounts of an oligomeric hydrolyzate from methyltrimethoxysilane in a blend with an adhesion promoter. However, the cured compositions have the disadvantage that, at high temperatures and very high relative humidities, they can lose some of their elasticity. This manifests itself in a reduced rubber hardness in particular. How this loss of elasticity may be prevented for these compositions has hitherto not been shown.